This program was a three-phase effort. Phase I was devoted to evaluatiing compatible fiber surface finishes for thermoplastic matrices. Three polysulfone resins (P-1700, PKXA.41 and PKXA.24) from Union Carbide were evaluated. Under Phase II graphite reinforced thermoplastic composites were evaluated for stress cracking in various service environments. Methods were also studied for providing a protective metallic or polymeric clad surface on the thermoplastic laminates. Specimens were exposed to various aircraft fluids and then tested for residual properties. Phase III of the program was devoted to hybridizing graphite reinforced thermoplastic laminates with Kevlar and glass reinforcements. The structural potential of the hybrid systems was assessed before and after exposure to critical service environments. Three tests showed no deficiencies that would preclude the use of hybrids on structural components.